HIGH-RESOLUTION STUDY OF THE FIRST STRETCHING OVERTONES OF (H3SIBR)-BR-79

The Fourier transform infrared spectrum of monoisotopic (H3SiBr)-Br-79 (resolution 7.7 x 10(-3) cm(-1)) was studied from 4200 to 4520 cm(-1) , in the region of the first overtones of the Si-H stretching vibratio n. The investigation of the spectrum revealed the presence of two band systems, the first consisting of one parallel (upsilon(0) = 4340.2002 cm(-1)) and one perpendicular (upsilon(0) = 4342.1432 cm(-1)) strong component, and the second of one parallel (upsilon(0) = 4405.789 cm(-1 )) and one perpendicular (upsilon(0) = 4416.233 cm(-1)) weak component . The rovibrational analysis shows strong local perturbations for both strong and weak systems. Seven hundred eighty-one nonzero-weighted tr ansitions belonging to the strong system [the (200) manifold in the lo cal mode picture] were fitted to a simple model involving a perpendicu lar component interacting by a weak Coriolis resonance with a parallel component. The most severely perturbed transitions (whose \obs-calc\ values exceeded 3 x 10(-3) cm(-1)) were given zero weights. The standa rd deviations of the fit were 1.0 x 10(-3) and 0.69 x 10(-3) cm(-1) fo r the parallel and the perpendicular components, respectively. The wea k band system, severely perturbed by many ''dark'' perturbers, was fit ted to a model involving one parallel and one perpendicular band, conn ected by a Coriolis-type resonance. The K'' . Delta K = +10 to +18 sub bands of the perpendicular component, which showed very high observed - calculated values (similar to 0.5 cm(-1)), were excluded from this c alculation. The standard deviations of the fit were 11 x 10(-3) and 13 x 10(-3) cm(-1) for the parallel and the perpendicular components, re spectively. (C) 1998 Academic Press.